When early versions of 10.5 tried to request an SRV record from these servers, some would be smart enough to reply with a “can’t do it” (triggering the OS to request an A record instead), but others wouldn’t respond at all. And so the OS would wait 30 seconds (default timeout for name lookups unless overridden by apps) and then try again. After a few SRV failures, the OS would revert to an A record request. But by then most users had either cancelled the request or fallen asleep. #

The “fix” was that Apple reverted the DNS lookup behavior in 10.5.3 to way lookups were done in 10.4 and earlier – via “A” records.